1. Field of the Invention
The present invention relates to an image display device and an operating method thereof.
2. Discussion of the Related Art
In recent years, image display device products having miniaturized and lightweight features, as well as powerful performance, have been produced.
The cathode ray tube (CRT) that has been widely used as an information display device has many advantages from the viewpoint of performance and price, but it also has many disadvantages from the viewpoint of miniaturization and portability.
On the contrary, the liquid crystal display device (LCD) has become a popular substitute for the CRT because of their small size, light weight and low power consumption. Thus, LCD devices have been employed in almost all information processing devices.
The LCD is driven by using the optical anisotropy and polarization properties of the liquid crystal material in the display. Because the liquid crystal molecules are thin and long, the arrangement direction of liquid crystal molecules may be controlled by selectively applying an electric field to the liquid crystal molecules having directionality and polarity. Accordingly, when the alignment direction is selectively controlled, the optical anisotropy of the liquid crystal causes the light to be transmitted or blocked along the arrangement direction of the liquid crystal molecules. In this manner, the color and image are displayed.
FIG. 1 illustrates an exploded perspective view of a related art LCD.
Referring to FIG. 1, the LCD includes a liquid crystal panel 5 and a backlight assembly 10. The liquid crystal panel 5 includes an array substrate on which a plurality of pixels are arranged in a matrix configuration, and a color filter substrate on which a plurality of red (R), green (G), and blue (B) color filters are arranged in a matrix configuration. The liquid crystal panel 5 and the backlight assembly 10 are stacked on top of one another in a molded frame 21.
A gate printed circuit board (PCB) 7 for applying a driving signal is disposed at one edge of the liquid crystal panel 5, and a data PCB 9 for applying a graphic signal is disposed at another edge of the liquid crystal panel 5.
The backlight assembly 10 is disposed below the liquid crystal panel 5. The backlight assembly 10 includes a plurality of optical sheets 11, a lamp 13 for generating light for image display, a light guide plate 160 converting the light generated from the lamp 13 into a surface light having an area corresponding to the size of the liquid crystal panel 5, and a reflection plate 17 for reflecting upwards the light leaked through the light guide plate 15 to enhance light efficiency.
The backlight assembly 10 and the liquid crystal panel 5 are stacked and inserted into the mold frame 21 so as to protect the backlight assembly 10 and the liquid crystal panel 5 from an external impact. Also, in order to prevent the liquid crystal panel from shaking, a guide panel 3 is provided to fix the liquid crystal panel 5 in place.
Also, the mold frame 21 that receives the liquid crystal panel 5 and the backlight assembly 10 is coupled to a case top 1 and a bottom cover 22, respectively.
FIG. 2 illustrates a schematic view of the backlight assembly according to the related art.
Referring to FIG. 2, the lamp 13 is disposed on an edge of the light guide plate 15 and fixed by a lamp housing 13a. 
The light guide plate 15 becomes thinner from a light incidence region to a light emission region. The optical sheets 11 including a diffusion sheet and a prism sheet are stacked onto the light guide plate 15.
The lamp 13 is fixed at the light incidence region of the light guide plate 15 by the lamp housing 13a, and the lamp housing 13a is attached on and fixed to an edge of the light incidence region of the light guide plate 15.
Light that is incident from the lamp 13 is reflected toward the light emission region of the light guide plate 15 by the prism sheet disposed above or below the light guide plate 15 and progresses toward an upper direction of the light guide plate 15.
The reflection plate 17 disposed below the light guide plate 15 reflects the light travelling from the bottom of the light guide plate 15 toward the optical sheets 11.
The diagrammatic appearance of the light guide plate constructed as above is illustrated in FIGS. 3A and 3B. Specifically, FIG. 3A is a plane view of the general prism light guide plate and FIG. 3B is a sectional view of the light guide plate illustrated in FIG. 3A.
As illustrated in FIGS. 3A and 3B, the prism light guide plate 15 has a structure in which the bottom surface has a plurality of prisms continuously formed in a lateral direction with respect to a vertical center axis.
Thus, because a sectional structure of the prism light guide plate 15 at the light incidence region is the same as those at the light emission region, the light that is incident toward the light incidence region from the lamp 13 is reflected at a predetermined angle such that the reflected light is transferred to an overall area of the light guide plate 15.
The prisms disposed on the bottom surface of the prism light guide plate 15 have an angle inclined by less than 5 degrees in left and right directions with respect to a vertical central axis from the light incidence region to the light emission region. In other words, because the prisms are arranged almost parallel with one another, the light that is incident from the lamp 13 is reflected with a uniform angle throughout the whole area of the light guide plate 15.
However, the related art LCD having the above construction has a disadvantage that light efficiency is lowered because the light generated from the lamp of the backlight assembly is incident into the light guide plate, then converted into a surface light, and the converted surface light is radiated onto the liquid crystal panel to display an image. In other words, only 30% of the light generated from the lamp is used for image display of the liquid crystal panel.
Considering the above-described low light efficiency, development on more efficient image display device capable of solving the disadvantages of the related art image display device is desired.